Anyone Know How the Metro Gun Works?
Pretty much, it works for the same reason your 22 rifle is quieter than your 22 pistol. More metal allows less sound and gas to escape. But regarding the reported level of decibel reduction, folks at subguns note it’s a bit overstated:
The website claims 72 decibels which I thought was BS, so I wrote to them asking about their testing methods. They claimed the microphones were 100 feet away from the gun, meaning that the noise level recorded was less than 1/1000th of what it would be if recorded near the gun as required by the usual standards.
I’ve not actually heard one fired.